New Clues To World's Ozone Depletion*

London UK (SPX) Jul 29, 2007

Large quantities of ozone-depleting chemicals have been discovered in
the Antarctic atmosphere by researchers from the University of Leeds,
the University of East Anglia, and the British Antarctic Survey. The
team of atmospheric chemists carried out an 18-month study of the
make-up of the lowest part of the earth's atmosphere on the Brunt Ice
Shelf, about 20 km from the Weddell Sea. They found high concentrations
of halogens - bromine and iodine oxides - which persist throughout the
period when there is sunlight in Antarctica (August through May).

A big surprise to the science team was the large quantities of iodine
oxide, since this chemical has not been detected in the Arctic.

The source of the halogens is natural - sea-salt in the case of bromine,
and in the case of iodine, almost certainly bright orange algae that
coat the underside of the sea ice around the continent.

These halogens cause a substantial depletion in ozone above the ice
surface. This affects the so-called oxidising capacity of the atmosphere
- its ability to "clean itself" by removing certain - often man-made -
chemical compounds. The iodine oxides also form tiny particles (a few
nanometres in size), which can grow to form ice clouds, with a
consequent impact on the local climate.

Scientists now plan to carry out further research to assess what impact
this may be having on the local environment. Very recent satellite
observations by one of the team, Dr Alfonso Saiz-Lopez, have confirmed
that iodine oxides are widespread throughout coastal Antarctica.

John Plane, professor of atmospheric chemistry at the University of
Leeds, says: "Halogens in the lowest part of the atmosphere have
important impacts on ozone depletion, the ability of the atmosphere to
remove potentially harmful compounds, and aerosol formation. All these
atmospheric phenomena are linked to climate change. We still have to
work out what the ramifications of this discovery are. These exciting
results also show how important it is to keep exploring the atmosphere -
there seems to be plenty more to find out."

Using high-tech measuring equipment, a beam of light was projected
across the ice shelf and the spectrum of the reflected light analysed
and chemical levels measured. The work was carried out in a new
atmospheric observatory at Halley Station, operated by the British
Antarctic Survey, and was supported by funding from the U.K.'s Natural
Environment Research Council.